Journal of the American Mosquito Control Association
Vol. 4, No. 3
AEDES ALBOPICTUS IN THE UNITED STATES: RAPID SPREAD OF A
POTENTIAL DISEASE VECTOR
C. G. MOORE, D. B. FRANCY, D. A. ELIASON and T. P. MONATH
Division of Vector-Borne Viral Diseases, Center for Infectious Diseases, Centers for Disease Control, Public
Health Service, U. S. Department of Health and Human Services, P. 0. Box 2087, Fort Collins, CO 80522
ABSTRACT. Aedes albopictus, the Asian "tiger mosquito," was found in Houston, Texas, in 1985.
Aedes albopictus is primarily a forest edge inhabiting species that has readily adapted to the container
habitats produced by humans. Although not yet incriminated in the spread of any disease in the
Americas, it has been repeatedly implicated in epidemic dengue and dengue hemorrhagic fever transmis-
sion in Asia. It is a competent laboratory vector of La Crosse, yellow fever and other viruses, and can
transovarially transmit at least 15 viruses. In 1986, Ae. albopictus was found in many other Texas
counties, and in Alabama, Arkansas, Florida, Georgia, Illinois, Indiana, Louisiana, Mississippi, Missouri,
Ohio, and Tennessee. In 1987, infestations were discovered in Delaware, Kentucky, Maryland, and North
Carolina. Aedes albopictus and other exotic species were intercepted in shipments of used tires entering
the United States from Asia. All such tires must now be free of mosquitoes before entering the country.
Control over the movement and storage of tires, a strong source reduction program, and intensive public
education can solve the albopictus problem.
On August 2, 1985, the Harris County Mos-
quito Control District in Houston, Texas, dis-
covered that Aedes albopictus (Skuse), a mos-
quito of Asian origin, was established in Harris
County (Sprenger and Wuithiranyagool 1986).
The identification was confirmed by the U. S.
National Museum, and the Centers for Disease
Control (CDC) was notified of the infestation
on January 31, 1986. The CDC in turn notified
the appropriate state, federal, and international
agencies. Although Ae. albopictus had been col-
lected previously in the United States (Reiter
and Darsie 1984), this was the first report of
breeding populations established in this hemi-
This species, commonly known as the "Asian
tiger mosquito" (Robertson and Hu 1935), is
found from Madagascar eastward through Asia
to Japan, Korea, and northern China (Knight
and Stone 1977, Huang 1972). It is also present
In Asia, Ae. albopictus is primarily a forest
edge inhabiting species (Lu et al. 1980), giving
way to other Aedes species inside forested areas.
It has readily adapted to the container habitats
produced by humans. Aedes albopictus is not as
strongly dependent on humans as Ae. aegypti
(Linn.); it could colonize tree holes and other
similar habitats in the eastern United States,
making control extremely difficult.
Field and laboratory studies of competition
between tropical Asian strains of Ae. albopictus
and Ae. aegypti suggested that aegypti would
eliminate albopictus (Gilotra et al. 1967, Moore
and Fisher 1969). In Hawaii, however, the re-
verse happened (Usinger 1944), possibly because
aegypti is near the limit of its northern distri-
bution. Recent studies by Hawley et al. (1986)
indicate the U. S. strains of albopictus are of
northern Asian origin, and these strains may be
better adapted than aegypti to the more temper-
ate ecological conditions of the United States
(Nawrocki and Hawley 1987). Moreover, work-
ers in several states observe that albopictus is
Aedes albopictus has been repeatedly impli-
cated in epidemic dengue and dengue hemor-
rhagic fever transmission in Asia (Metselaar et
al. 1980, Jumali et al. 1979). Laboratory studies
also have confirmed its efficiency as a dengue
vector (Boromisa et al. 1987, Mitchell et al.
1987). This species is a competent vector of
California encephalitis group viruses (Shroyer
1986a, P. R. Grimstad et al., unpublished data),
yellow fever and epidemic polyarthritis (Ross
River) viruses (Mitchell and Gubler 1987,
Mitchell et al. 1987), and other agents (Shroyer
1986b). In addition, Ae. albopictus can transmit
transovarially at least 15 viruses (Shroyer
1986b); it is not an effective vector of St. Louis
or Venezuelan equine encephalitis viruses (D. B.
Francy, unpublished data).
Aedes albopictus has not yet been incriminated
in the spread of any disease in the Americas,
and probably will not be until the level of mos-
quito-reservoir and human-mosquito contact ex-
ceeds some threshold; the potential impact of a
vector such as Ae. albopictus in a new environ-
ment is difficult to predict. Although dengue
epidemics have occurred principally in the Gulf
Coast states, where Ae. aegypti already occurs, a
major Ae. aegypta'-transmitted dengue epidemic
occurred in Philadelphia in the late 18th century
(Wisseman and Sweet 1961, Anonymous 1977).
The presence of a new, competent vector in the
northern United States could mean a resurgence
of dengue in those areas. Of more immediate
concern is the presence of Ae. albopictus in La
Spread of Ae. albopictus in the United States
Crosse-endemic portions of the eastern United
States. Since that virus is already present, the
possibility of a vectorial role seems higher than
for other viruses. The ability of Ae. albopictus to
transmit yellow fever is of concern because the
species was introduced into Brazil in 1986 (Cen-
ters for Disease Control 1986b). This mosquito
can breed in areas removed from human habi-
tation and might serve as a link between jungle
and urban cycles of yellow fever.
We describe here the progressive movement
of Ae. albopictus in the United States in 1986
and 1987, as recorded by the Division of Vector-
Borne Viral Diseases (DVBVD), Centers for
Disease Control (CDC). State and local health
department and mosquito control agency per-
sonnel collaborated in this effort (CDC 1986a,
1986b, 1986c, 1987).
DISTRIBUTION AND SPREAD,
In their initial survey in Houston, August
through October 1985, Sprenger and Wuithir-
anyagool (1986) found that Ae. albopictus was
widespread, especially in the eastern half of
Harris county. They found the species in 73.9%
of water- filled containers with mosquito larvae.
In 1986, with the advent of warm weather and
spring rainfall, efforts were begun to determine
the extent of the infestation in Texas and sur-
rounding states. During April and May, Ae. al-
bopictus was found in counties adjacent to Hous-
ton; in New Orleans, Louisiana, and surround-
ing parishes; and in Memphis, Tennessee. In
June and early July, the mosquito was reported
from Gulfport, Mississippi, and Jacksonville,
Since 1981, CDC had maintained a collabo-
rative Aedes aegypti surveillance program, using
the CDC ovitrap (Fay and Eliason 1966). In
early 1986, the program was modified and ex-
panded to better detect Ae. albopictus. The pro-
gram involved 39 cities (Table 1), of which 10
were infested with Ae. albopictus. The species
was found in San Antonio, Texas, as a result of
the ovitrap program. In 1987, the program was
expanded to include 59 cities, of which 19 were
infested (Table 2). Again, one infested city was
found (in the absence of other surveillance) in
1987 as a result of the program.
A systematic survey of 41 cities and towns in
6 southern states was conducted in July 1986
(CDC 1986b). Because Ae. albopictus tends to
oviposit in discarded tires containing rainwater,
used-tire dumps and premises of tire dealers and
retreaders were surveyed. Aedes albopictus was
found to be widely disseminated in the southern
United States but to have a spotty and discon-
tinuous distribution (Table 3, Fig. 1A). In many
sites, Ae. albopictus was abundant and bit hu-
mans aggressively. The presence of Ae. aegypti
in an area did not appear to retard the ingress
of Ae. albopictus, which had replaced the former
in many locations.
From September 15-29, 1986, surveys were
conducted in Ohio, Indiana, Illinois, Missouri,
Kentucky, and Arkansas. Again mainly the busi-
ness premises of tire dealers and retreaders were
inspected. Ae. albopictus was found in at least 1
location in 2 of 10 counties surveyed in Illinois,
2 of 16 in Indiana, 3 of 11 in Missouri, and 1 of
7 in Arkansas; none were found in the Kentucky
survey. In early September, a single infested site
had been discovered by the Ohio Department of
Health in Darke County; no further infestations
were found during surveys in 5 other Ohio coun-
ties. Infestations in the northern states were less
common (13% of 53 counties) than in the heav-
ily-infested states of Texas, Louisiana, and Mis-
sissippi (89% of 35 counties surveyed).
Statewide surveys in 1987 were conducted pri-
Table 1. Collaborative ovitrap program for Aedes albopictus in the eastern United States, 1986.
Journal of the American Mosquito Control Association Vol. 4 No. 3
Table 2. Collaborative ovitrap program for Aedes albopictus in
the eastern United States,
marily by state and local agencies. Additional
infestations of Ae. albopictus were found in Del-
aware, Kentucky, North Carolina, and Mary-
land (Table 3, Fig. IB). Several counties that
were inspected and found negative in 1986 were
positive for Ae. albopictus in 1987, suggesting
expansion of the species rather than discovery
of preexisting foci.
In July and August 1987, 8 cities known to be
infested with Ae. albopictus in Texas, Louisiana,
Florida, Missouri, Tennessee, and Indiana were
surveyed in detail to determine how far the
mosquito had spread from the original foci of
introduction and how it was spreading. The
results of that study will be reported separately;
however, there was a notable decrease in the
dominance of Ae. albopictus (i.e., albopictus as a
percent of all container-breeding Aedes spp.)
with increasing distance from Houston, the first
known infested city in the United States (Table
Despite its rapid northward and eastward ex-
tension, Ae. albopictus has so far failed to move
into south Texas or south Florida. The mosqui-
to's current southern limit is between 29° and
30° north latitude. The photoperiodic response
that allows this species to enter diapause (Haw-
ley et al. 1987), making it uniquely adapted to
the northern temperature environment, may
also be limiting its southern spread. If this is
true, the introduction of strains from more
southerly locations in Asia could result in south-
ward extension of the species into Mexico and
Central America. The Brazilian populations of
Ae. albopictus (CDC 1986b) are apparently un-
able to enter diapause (G. B. Craig, Jr., personal
communication), and may therefore be able to
occupy much of tropical America.
INTERCEPTION OF USED TIRES
Aedes albopictus has been collected or inter-
cepted in the contiguous United States on 3
previous occasions (Reiter and Darsie 1984), but
breeding populations were not demonstrated.
Because of previous interceptions and the ap-
parent association of the Houston infestation
with used tires, CDC began a program of in-
specting used auto and truck tires entering
U.S. ports from Asia. Of 3.2 million used tires
imported into the United States in 1985, 2.8
million came from Asian countries with indige-
nous Ae. albopictus populations. In 1986, more
than 22,000 tires were inspected by CDC, state,
and local personnel. On October 6-7, 1986, for
example, inspectors checked 2,613 tires in 9
cargo containers originating in Japan and off-
loaded in Seattle, Washington. Aedes albopictus
larvae were found in 11 tires in 2 of the con-
tainers (CDC 1986c). The positive containers
were fumigated with methyl bromide to kill lar-
vae and eggs. The 1986 inspections produced 15
tires with mosquito larvae of 5 species belonging
to 4 genera (Craven et al. 1988).
In 1987, staff of the Alameda County Mos-
quito Abatement District collected Ae. albopictus
larvae from large equipment tires shipped from
Hawaii to an Oakland, California, tire dealer.
No additional specimens have been collected at
the Oakland site, suggesting that the species
failed to become established.
Because this mosquito can introduce several
exotic arboviruses into the United States (via
transovarially infected eggs or larvae) and con-
tinued importation of populations from other
areas can expand the genetic variability of ex-
Spread of Ae. albopictus in the United States
Table 3. Aedes albopictus-mtested counties reported to CDC by state and local agencies, 1986 and 1987.
State & County
State & County
E. Baton Rouge
"+" - positive; "-" = negative; "±" = positive, but population was eradicated or area became negative
without treatment; "?" = unknown, not surveyed.
isting populations, additional introductions
must be prevented. On January 1, 1988, under
the provisions of Public Law 78-410, Public
Health Service Act, Section 361, and 42 CFR
71.32(c)(10), CDC required that all used tire
casings from Asia be certified as dry, clean, and
free of insects. The CDC is now monitoring
compliance with this regulation.
OPTIONS FOR CONTROL
Dealing with existing U. S. A. populations of
Ae. albopictus is more difficult than preventing
continued introductions from other countries.
Responses by different state and local agencies
have varied from no action to attempted eradi-
cation of foci. Permanent solutions are unlikely
as long as used tires are moved freely in inter-
state commerce without some disinsectization
requirement. One relatively inexpensive way to
reduce the spread of Ae. albopictus is to require
that tires be stored and shipped without water.
Insecticide susceptibility tests by the New
Orleans Mosquito Control Board, Rutgers Uni-
versity, Harris County Mosquito Control Dis-
trict, and DVBVD show that this mosquito has
Journal of the American Mosquito Control Association Vol. 4, No. 3
Fig. 1. Distribution of the Asian "tiger mosquito," Aedes albopietus in the United States. A-1986, B-1987.
increased tolerance to bendiocarb, malathion, be considered by agencies using the foregoing
and temephos, among a limited number of in- compounds. A strong source reduction program
secticides tested to date. Rapid selection for and intensive public education can solve the
resistance under operational conditions should albopietus problem.
Spread of Ae. albopictus in the United States
Table 4. Dominance of Aedes albopictus among
container-breeding Aedes and distance from the
presumed focus of introduction into the United
as percent of
all Aedes spp.
We thank the 200 workers from 111 state and
local health, mosquito control, university, and
other agencies (identified in CDC 1986a, 1986b,
1986c, 1987) for their collaboration; all those
who helped gather these data; C. J. Bozzi, E. G.
Campos, R. B. Craven, W. L. Jakob, B. Pafume,
DVBVD, Fort Collins; and CDC summer survey
team leaders L. Harrel, W. Hawley, R. Kilgen,
A. Lowichik, J. Prullage, C. Pumpuni, and D.
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